Dr Phin said: "We tried to follow up contacts as much as possible, but it can be difficult – particularly if people don't have details you can contact them with.

"It is possible there may be other cases, these are definitely the first two we have picked up and at the moment there are two."

The bacterium Neisseria gonorrhoea has rapidly developed resistance to new antibiotics.

There have been growing levels of super-gonorrhoea around the world with similar cases reported in Japan, Canada and Australia.

Dr Olwen Williams, president of the British Association for Sexual Health and HIV, said: "We are deeply concerned by these new developments."

Paddy Horner, from the University of Bristol, told the BBC: "We've got to wait and see what happens over next few months and whether more cases appear, but it is only a matter of time before it arrives in the UK.

"When people mix sexually it can spread quite rapidly and the concern is this could become established – if not from this infection, then one in the future.